Method of manufacturing nano-template for a high-density patterned medium and high-density magnetic storage medium using the same

ABSTRACT

Disclosed is a method for manufacturing a template for a high-density patterned medium and a high-density magnetic storage medium using the same. In the method, magnetic particles are used as a mask and no lithographic process is required.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This is a divisional application of U.S. Ser. No. 11/781,391 filed onJul. 23, 2007 (now allowed), which claims priority from Korean patentapplication 10-2006-0084203, filed on Sep. 1, 2006, all of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a method for manufacturing anano-template which is suitable for fabricating a high-density patternedmedium and a high-density magnetic storage medium using the same.

2. Description of the Related Art

There is an increased demand for a record medium which is capable ofstoring mass information including moving pictures and has a highportability. It is also demanded that users who carry the record mediumhave an ability to access to and use the stored information.

Portable memory devices may be largely classified into a solid-statememory device such as a flash memory and a disk-type memory device suchas a hard disk. Since the solid-state memory device is expected to bedeveloped to have a maximum capacity of several gigabytes (GBs) in thenext several years, it is difficult to use the solid-state memory deviceas a large scale data storage device. On the other hand, even though thehard disk mounted on a portable device is expected to have a capacity ofseveral tens of GBs in the near future, it is also anticipated to bedifficult to achieve magnetic recording density of more than the severaltens of GBs.

In order to overcome such limitations, a method for manufacturing alarge-capacity high-density patterned medium has been proposed. E.g.,U.S. Pat. No. 7,041,394. U.S. Pat. No. 7,041,394 reports a method whichincludes forming a locking pattern in a medium substrate and filling thelocking pattern with a magnetic particle having a size of less than 0.1micrometer (i.e., less than 100 nanometer). The locking pattern isformed by lithography. In manufacturing a large-capacity high-densitypatterned recording medium, a use of a pattern template makes itpossible to simplify the manufacturing process of the recording mediumand increase a recording density of the medium.

A conventional template, which is used to manufacture a high-densitypatterned medium, will now be described.

FIG. 1 is a picture of a conventional template, which is used tomanufacture a high-density patterned medium, and FIG. 2 is a picture ofhigh-density patterned medium manufactured by using the template shownin FIG. 1.

As shown in FIGS. 1 and 2, a high-density patterned medium can bemanufactured by forming a pattern 10, which is etched in a substrate,and by filling the pattern 10 with a nanomaterial 20. The pattern 10 maybe formed by lithography. The nanomaterial may be chemically synthesizedparticles and completely fills the pattern.

The capacity of high-density patterned medium manufactured by using aconventional template, for example one reported in U.S. Pat. No.7,041,394, depends on the size of a formed pattern 10. That is, as thesize of the pattern 10 gets smaller, a higher-density patterned storagemedium can be manufactured.

However, it is very difficult, with the current lithography technology,to form a fine pattern with a width of less than tens of nanometers.Particularly, it is difficult to form a fine pattern of nanometer sizeover a broad region of a large capacity by means of the electron beam orphoto-lithography technology. It takes a long period of time touniformly form a fine pattern in a broad region of a medium substrateand productivity is degraded, so that there is a limitation to use thelithography technology for mass production of the pattern and/orrecording medium.

SUMMARY OF THE INVENTION

The present invention provides a method for forming a nano-template fora high-density patterned medium, which enables mass production of alarge-capacity high-density patterned medium, without using thelithography process for forming a fine pattern.

The present invention provides a high-density magnetic storage mediummanufactured by using the method which does not employ the lithographyprocess for forming a pattern.

In one embodiment of the present invention, there is provided a methodfor forming a template for a high-density patterned medium, the methodincludes: providing a substrate having a surface; applying a colloidalsolution of magnetic particles to the surface of the substrate, thecolloidal solution including a solvent and the magnetic particles;forming an uniform arrangement of the magnetic particles on thesubstrate by applying a magnetic field in a direction of perpendicularto the surface of the substrate; forming a magnetic particle layer onthe substrate by removing the solvent from the surface of the substrate;etching the substrate by using nanoparticle layer as a mask; andremoving the magnetic particles from the substrate.

The particles may be formed of one metal selected from the groupconsisting of Co, CoPt, CoP, CoPtCr, and an alloy thereof.

The magnetic field is applied by magnets positioned above and/or belowthe substrate. In one embodiment of the present invention, the magnetmay be an electromagnet disk which has coils arranged concentricallythereon.

In one embodiment of the present invention, the substrate may be in theform of a disk and have radial tracks of protrusions.

In another embodiment of the present invention, the substrate may have ahard mask layer on its surface. In such case, the method furtherincludes etching the hard mask layer before the substrate etching.

In accordance with another aspect of the present invention, there isprovided a high-density magnetic storage medium including: a substratehaving a surface; a perpendicular magnetic recording layer formed on thesubstrate; and a magnetic particle layer in which magnetic particles arearranged to form a pattern on the perpendicular magnetic recordinglayer.

In one embodiment, the perpendicular magnetic recording layer may beformed of a nanomaterial including CoCrPt.

In an embodiment of the present invention, the particle layer is formedof nanoparticles having an identical magnetic anisotropy which isperpendicular to the surface of the substrate. The nanoparticles mayhave an average diameter ranging several to several tens of nanometersand may have a cylindrical or cubic shape.

The nanoparticles may be formed of a metal selected from the groupconsisting of Co, CoPt, CoP, CoPtCr, and an alloy thereof. Thenanoparticles are arranged into a pattern by application of a magneticfield. The magnetic field is applied in a direction of perpendicular tothe surface of the substrate, on which the particles are placed.

In one embodiment of the present invention, a perpendicular magneticrecording layer may be formed on a surface of the substrate. Thesubstrate and the perpendicular magnetic recording layer may be in theform of a disk and may have radial tracks of protrusions formed on theperpendicular magnetic recording layer. In the embodiment, thenanoparticles are located between the radial tracks of the protrusions.Therefore, the high-density magnetic storage medium has an alternatingconcentric circles of protrusions and concentric circles of magneticparticles.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a picture of a conventional template for a high-densitypatterned medium, which is used to manufacture a high-density patternedmedium;

FIG. 2 is a picture of high-density patterned medium manufactured byusing the template shown in FIG. 1;

FIG. 3 is a flowchart illustrating a method of forming a nano-templatefor a high-density patterned medium according to an embodiment of thepresent invention;

FIG. 4 is a view illustrating an exemplary step of applying ananoparticle colloidal solution to a substrate according to anembodiment of the present invention;

FIG. 5 is a schematic sectional view illustrating an arrangement ofnanoparticles on a substrate by action of a pair of disk-shaped magnets,each positioned above and below the substrate;

FIGS. 6 and 7 are views illustrating the structure of coils in themagnets shown in FIG. 5;

FIG. 8 is a view illustrating the movement and arrangement ofnanoparticles on the substrate in FIG. 5, by the action of the pair ofdisk-shaped magnets;

FIG. 9 is a schematic sectional view illustrating the structure of asubstrate provided with radial tracks of protrusions, in whichnanoparticles are located in the recessed track formed between theprotrusions;

FIGS. 10A and 10B are cross-sectional views illustrating an exemplarysubstrate etching step;

FIGS. 11A to 11C are cross-sectional views illustrating an exemplarysubstrate etching step which uses a hard mask layer; and

FIG. 12 is a cross-sectional view illustrating the structure of ahigh-density magnetic storage medium which includes a perpendicularmagnetic recording layer and nanoparticles formed on the perpendicularmagnetic recording layer, in which the perpendicular magnetic recordinglayer and the nanoparticles have same magnetic anisotropy.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription and drawings, the same reference numerals are used todesignate the same or similar components, and so repetition of thedescription on the same or similar components will be omitted.

FIG. 3 is a flowchart illustrating a method for forming a nano-templatefor a high-density patterned medium according to an embodiment of thepresent invention, and FIG. 4 to FIG. 11C are views illustrating eachstep shown in FIG. 3.

As shown in FIG. 3, according to the method for forming a nano-templatefor a high-density patterned medium, a colloidal solution includingnanoparticles is applied to a substrate (step 110).

FIG. 4 is a view illustrating a step of applying a nanoparticlecolloidal solution to a substrate based on the method for forming thenano-template for a high-density patterned medium according to anembodiment of the present invention.

The nanoparticle colloidal solution 110 is applied to the substrate 120by dipping method or a spin coating method. This method may be usedafter coating self-assembly monolayer(SAM). The application may berepeated several times until a desired density of nanoparticles on thesurface of the substrate 120 is obtained.

The nanoparticle colloidal solution 110 may be formed by injecting ormixing nanoparticles 111 into or with a proper carrier. The propercarrier may include, but are not limited to, a colloidal solvent or aresist solution for lithography. The nanoparticles are formed from ametal material selected from the group consisting of, for example, Co,CoPt, CoP, CoPtCr, and an alloy thereof. In this case, it is possible touse nanoparticles 111 having sizes ranging from several to several tensof nanometers.

FIG. 5 is a FIG. 5 is a schematic sectional view illustrating anarrangement of nanoparticles on a substrate by action of a pair ofdisk-shaped magnets, each positioned above and below the substrate.FIGS. 6 and 7 are views illustrating the structure of coils in themagnets shown in FIG. 5, and FIG. 8 is a view illustrating the movementand arrangement of nanoparticles on the substrate in FIG. 5, by theaction of the pair of disk-shaped magnets.

As shown in FIGS. 5 to 8, the substrate 120, which has nanoparticlescoated on its one surface, is inserted between the pair of disk-shapedmagnets 210 and 220, which are arranged in parallel to each other toform a magnetic field in a transverse direction between the magnets 210and 220, so that the magnetic field is applied to the nanoparticles in adirection perpendicular to the surface of the substrate 120 (step 120).

In on embodiment, as shown in FIGS. 6 and 7, the disk-shaped magnets 210and 220 include electromagnets which have ring-shaped coils. The coils211, 212, and 213 have different radiuses r1, r2 and r3, respectively,and each generate a magnetic field “B” when current “i” is applied tothem. In one embodiment, the coils of one magnet 210 may be positionedin corresponding tracts to those of the coils of the other magnet 220.In other embodiment, the coils of one magnet 210 may be positioned toform alternating tracks with respect to the coils of the magnet 220.

In one embodiment, the substrate 120 is disposed horizontally betweenthe pair of disk-shaped magnets 210 and 220 which form a magnetic fieldin the transverse (or vertical) direction between the disk-shapedmagnets 210 and 220, and the nanoparticles 111 on the substrate 120 arearranged on the substrate 120 in a form of concentric circles or radialtracks which each correspond to the respective coils of the magnets 210and 220.

FIG. 8 is a view illustrating an operation in which nanoparticles 111 onthe substrate are arranged in a form of concentric circles by the pairof disk-shaped magnets 210 and 220. As indicated by arrows in anenlarged portion of FIG. 8, the nanoparticles 111 on the substrate 120are moved to and are arranged along the electromagnetic tracks on thesubstrate 120, which each correspond to the coils 211, 212, and 213.

FIG. 9 is a is a schematic sectional view illustrating the structure ofa substrate provided with radial tracks of protrusions, in whichnanoparticles are located in the recessed track formed between theprotrusions.

As shown in FIG. 9, the protrusions 140 may be formed as concentriccircles or radial tracks on a surface of the substrate, and thenanoparticles 111 may be placed and arranged on the surface of thesubstrate 120 between the concentric circles of protrusions 140. Theprotrusions 140 may be formed before the nanoparticle colloidal solutionis applied to the substrate 120. In one embodiment, the concentriccircles or radial tracks of the protrusions 140 are formed on thesurface of the substrate 120 in such a way that they each correspond tothe positions of coils of the electromagnets of the pair of disk-shapedmagnets, so that the nanoparticles 111 are arranged between theprotrusions 140. The circles of protrusions may be formed by knownmethods, including lithography methods and may be made from variousmaterials such as a polymer, an insulator, a metal, etc. The concentriccircles or radial circles of protrusions improve the uniform arrangementof the magnetic particles on the substrate. Owing to a magnetic fieldapplied in a direction of perpendicular to the substrate by the pair ofdisk-shaped magnets, the nanoparticles are arranged to have theidentical magnetic anisotropy. The magnetic anisotropy includes a shapemagnetic anisotropy and a crystal magnetic anisotropy. When thenanoparticles have a sphere shape or symmetrical shape, only the crystalmagnetic anisotropy exerts an influence as a principal factor.

However, the nanoparticles, which are arranged to have the identicalmagnetic anisotropy by the magnetic field as described above, cannot beused as a high-density patterned medium as they are, because thenanoparticles lose the magnetic anisotropy when the pair of disk-shapedmagnets is removed, causing the magnetic field applied to the substrateto disappear.

After the nanoparticles have been uniformly arranged on the substrate bythe magnetic field as described above, the colloidal solution is removedto leave nanoparticles on the substrate, forming a nanoparticle layerpattern (step 130). This may be done by drying.

FIGS. 10A and 10B are cross-sectional views illustrating a substrateetching step based on the method for forming a nano-template for ahigh-density patterned medium according to an embodiment of the presentinvention.

As shown in FIGS. 10A and 10B, when the substrate 120 is etched by usingthe nanoparticles 111 as a mask (step 140), the pattern of thenanoparticle layer is transcribed on the substrate, so that a substratenano-pattern 121 having the shape of nanoparticles is formed on thesubstrate 120. The etching may be performed by known methods, such as aplasma dry etching or plasma ion etching (RIE) scheme.

Then, the nanoparticles 111 used as a mask are removed from thesubstrate 120 to provide a nano-template (or a nano-master ornano-mold), having a nano-pattern 121 which corresponds to thearrangement of the nanoparticles (step 150).

By using the nano-template, which is produced as described above, itbecomes possible to mass-produce a high-density patterned medium havinga pattern of which width is tens of nanometers or less.

FIGS. 11A to 11C are cross-sectional views illustrating an exemplarysubstrate etching step using a hard mask layer, according to anembodiment of the present invention.

During a substrate etching process using the nanoparticles 111 as amask, there may be difficulty in etching the substrate 120 by using thenanoparticles 111 as a mask, because of a too small size ofnanoparticles or a poor etching selectivity with respect to thesubstrate. In this case, preferably, as shown in FIGS. 11A to 11C, ahard mask layer 130 (e.g., a silicon oxide layer or silicon nitridelayer) having a material different from the metallic nanoparticles isformed on the surface of the substrate before the nanoparticle colloidalsolution is applied to the surface of the substrate, and the hard masklayer 130 is etched by using the nanoparticles 111 as a mask to providea hard mask pattern 131 on the substrate 120.

When the hard mask layer 130 is used as a layer for patterntranscription, as described above, the arranged pattern of thenanoparticles is transcribed on the hard mask layer 130, and thesubstrate 120 is etched by using a hard mask pattern 131. This providesan advantage in that the process is easy.

Then, when the substrate 120 is etched by using the hard mask pattern131 as a mask, the same substrate nano-pattern 121 as that formed whenthe etching process is performed by using the nanoparticles 111 as amask is formed on the substrate 120. In this case, the nanoparticles 111and the hard disk pattern 131, which are used as an etching mask, may beeasily removed by a known method.

The above-mentioned method for forming a nano-template may also be usedto produce a high density magnetic storage medium. A method andstructure of such a high density magnetic storage medium will bedescribed below. In one embodiment, a magnetic field is applied in adirection of perpendicular to the substrate by a pair of disk-shapedmagnets, each positioned below and above the substrate, respectively, sothat nanoparticles on the substrate can be arranged to have the samemagnetic anisotropy, and the arranged state of the nanoparticles can becontinuously maintained.

FIG. 12 is a cross-sectional view illustrating the structure of ahigh-density magnetic storage medium which is arranged to have the samemagnetic anisotropy by a magnetic field applied to a substrate accordingto an embodiment of the present invention.

As shown in FIG. 12, the high-density magnetic storage medium accordingto an embodiment of the present invention includes a substrate 120, aperpendicular magnetic recording layer 150, and a nanoparticle layer.

The substrate 120 serves as a supporter to form the high-densitymagnetic storage medium, and the perpendicular magnetic recording layer150 is formed on the substrate 120. The perpendicular magnetic recordinglayer 150 may have a structure of a CoCrPt film deposited on thesubstrate 120, or a structure of a CoCrPt film formed on a filmincluding Ru and Ta. The perpendicular magnetic recording layer 150 maybe a single layer or laminate of multiple layers. The perpendicularmagnetic recording layer has a thickness of tens of nanometers.

A nanoparticle colloidal solution is applied to the top of theperpendicular magnetic recording layer 150, which has been formed on thesubstrate 120 as described above. The nanoparticle colloidal solution110 may be formed by injecting or mixing nanoparticles 111 into or witha proper carrier. The proper carrier may include, but are not limitedto, a colloidal solvent or a resist solution for lithography. Thenanoparticles are formed from a metal material selected from the groupconsisting of, for example, Co, CoPt, CoP, CoPtCr, and an alloy thereof.In this case, it is possible to use nanoparticles 111 having sizesranging from several to several tens of nanometers. The nanoparticleshave a symmetrical shape such as a cylindrical crystal structure orcubic crystal structure. They have a magnetic anisotropy perpendicularto the substrate 120.

Then, similarly to the above-mentioned method for forming anano-template for a high-density patterned medium, a magnetic field isapplied in a direction of perpendicular to the substrate 120 by a pairof disk-shaped magnets 210 and 220, which are positioned below and abovethe substrate, respectively, so that nanoparticles included in thenanoparticle colloidal solution are uniformly arranged to form apattern, which corresponds to an electromagnetic force applied by coilsof the magnets. In one embodiment, the pattern is plural concentriccircles or radial tracks. Also, by the magnetic field appliedperpendicularly to the substrate, both of the perpendicular magneticrecording layer 150 and the nanoparticles 111 are arranged to have thesame magnetic anisotropy.

In one embodiment, the disk-shaped magnet is an electromagnet, in whicha plurality of coils are arranged in a form of concentric circles, asshown in FIG. 7, so that nanoparticles on the substrate can be uniformlyarranged on the substrate by current applied to the coils.

According to the high-density magnetic storage medium including thenanoparticle layer, which has been formed by the method based on thepresent invention, both of the perpendicular magnetic recording layer150 and the nanoparticles 111 are arranged to have the same magneticanisotropy, and the magnetic anisotropy of the nanoparticles ismaintained by interaction between the perpendicular magnetic recordinglayer 150 and the nanoparticles 111 even after the magnetic fieldperpendicular to the substrate has been removed.

The nanoparticle layer may be fixed by evaporating the solvent of thecolloidal solution. A passivation layer may be formed on the top of thenanoparticle layer. The passivation layer may be made from one selectedfrom the group consisting of carbon, AIN, Si₃N₄, MgO, Al₂O₃, TiN, andTiC.

Therefore, the high-density magnetic storage medium according to thepresent invention, which can maintain the magnetic anisotropy asdescribed above, includes a nanoparticle layer having a magneticanisotropy perpendicular to the substrate. The nanoparticle layer formedof nanoparticles can be used as a storage unit with a size of severaltens of nanometers or less, thereby being used as a large-capacityhigh-density magnetic storage medium.

In addition, when a substrate has protrusions as described withreference to FIG. 9, the protrusions may be arranged in a form ofconcentric circles or radial tracks and may be formed on a hard masklayer on the substrate. The protrusions, which may be arranged in a formof concentric circles at locations corresponding to those of theelectromagnet of the disk-shaped magnet, enable the nanoparticles to bemore uniformly arranged in a form of concentric circles on thesubstrate.

The nano-template forming method according to various embodiments of thepresent invention has the following effects.

According to the method for forming a nano-template for a high-densitypatterned medium, a pattern having a size of tens of nanometers or lesscan be easily formed on the nano-template by using nanoparticlesarranged on the substrate without a lithography process, therebyachieving a high storage density for large capacity recording media.

A high-density magnetic storage medium with a nanoparticle layer, whichmaintains a magnetic anisotropy, may be fabricated, without using alithography process, so that a large-capacity storage medium can beeasily realized.

Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A method for forming a high-density magnetic storage medium, themethod comprising: preparing a substrate having a surface; forming aperpendicular magnetic recording layer on the surface of the substrate;applying a colloidal solution of magnetic particles to the perpendicularmagnetic recording layer, the colloidal solution comprising a solventand the magnetic particles; arranging the magnetic particlesconcentrically on the perpendicular magnetic recording layer by applyinga magnetic field perpendicular to the substrate; and forming a magneticparticle layer on the perpendicular magnetic recording layer by removingthe solvent of the colloidal solution from the perpendicular magneticrecording layer, wherein the mangetic field perpendicular to thesubstrate is provided by magnets installed above and below the substrateand wherein each of the magnets comprises a coil which is arranged in aform of concentric circles.
 2. The method as claimed in claim 1, whereinthe substrate has protrusions which are arranged in a form of concentriccircles.